Understanding automatic key frames insertion
The red button in the timeline enables the Auto Keyframe function.

 

By default, autokeyframe will create a LocRotScale keyset. So even if you changed only one thing and left the rest untouched, it will create 9 keyframes, one for each axis of the Location, Rotation and Scale.



If you only want to record a specific channel with autokeyframe (for example rotation, but not Location or Scale) you can create a different keyset by left clicking here:



And enabling "use Active Keying Set Only"



Your changes will only be recorded for the current Keying set.



You can temporarily disable the use of "Active Keying Set Only" and make changes in other channels (like location for example) and the autokeyframe will revert to the default behavior of recording LocRotScale.